Energy Resources. Assosciate Professor

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1 Energy Resources Dr. Fahad Noor Assosciate Professor Engr. Adnan Qamar Lecturer

2 Hydro Power Hydropower energy is ultimately derived from the sun, which drives the water cycle. In the water cycle, rivers are recharged in a continuous cycle. 12/14/2018 2

3 Hydro Power 12/14/2018 3

4 Hydro Power 12/14/2018 4

5 Hydro Power Hydro-power is by far the most established and widely used renewable resource for electricity generation and commercial investment. The capacity of total worldwide installations has grown at about 5% per year since. Hydro-power now accounts for about 20% of world s electric generation. Output depends on rainfall and the terrain. In about one-third of the world countries, hydro-power produces more than half the total electricity. 12/14/2018 5

6 Hydro Power 12/14/2018 6

7 Hydro Power (Benefits) Hydro installations and plants are long-lasting with routine maintenance, e.g. turbines for about fifty years and longer with minor refurbishment, dams and waterways for perhaps hundred years. Long turbine life is due to the continuous, steady operation without high temperature or other stress. 12/14/2018 7

8 Hydro Power (Drawbacks) Possible adverse environmental impact on fish Silting of dams Corrosion of turbines in certain water conditions Social impact of displacement of people from the reservoir site Loss of potentially productive land Relatively large capital costs compared with those of fossil power stations. Considerable civil engineering (in the form of dams, pipe work, etc.) is always required to direct the flow through the turbines. 12/14/2018 8

9 Hydro Power (Principles) A volume per second, Q, of water falls down a slope. The density of the fluid is ρ. Thus the mass falling per unit time is ρ.q, and the rate of potential energy lost by the falling fluid is where g is the acceleration due to gravity, P 0 is the energy change per second (a power measured in Watts) and H is the vertical component of the water path. 12/14/2018 9

10 Hydro Power Question No 1 Following details are available for Ghazi Barotha Dam Generation capacity 1450 MW (5 units each with 290 MW capacity) Head available 69 m Flow available 2340 m 3 /s (468 m 3 /s for one turbine-generator set) Construction cost 2.1 Billion US-Dollar Reservoir capacity 25,500,000 m 3 Calculate how much is theoretical potential harnessed practically. and what fraction is being 12/14/

11 Hydro Power Question No 2 Re-read question number 1, consider capital cost for twenty years time with an annual interest rate of 5%. Consider operation and maintenance cost to be about 4% of annualized cost. Calculate cost per kwh of electricity produced (Consider 1 USD=105 PKR). 12/14/

12 Hydro Power Question No 3 Following information is available for Tarbela dam, Installed capacity (3478 MW, total 14 units, 10 Units of 175 MW each and 4 units of 432 MW each). Following table summarizes annual power harnessed from this plant. Do the calculations and compare how much of installed capacity was actually harnessed from Year Produced power (Million kwh) Mention reasons why actual power production is significantly less than that of installed capacity. 12/14/

13 Hydro Power (Principle) Unlike some other power sources, there is no fundamental thermodynamic or dynamic reason why the output power of a hydro-system should be less than the input power P 0, apart from frictional losses which can be proportionately very small. The main disadvantage of hydro-power is that the site must have sufficiently high Q and H. In general this requires a rainfall > 40 cmy 1 dispersed through the year, a suitable catchment and, if possible, a water storage site. 12/14/

14 Hydropower resource assessment Measurement of Head For nearly vertical falls, trigonometric methods (perhaps even using the lengths of shadows) are suitable; whereas for more gently sloping sites, the use of level and pole is straightforward. The power input to the turbine depends not on the geometric (or total) head H t as measured this way, but on the available head Ha: 12/14/

15 Hydro Power Losses at canal entrance Losses due to contraction and expansion Losses due to friction Losses due to trash rack Losses due to bend 12/14/

16 Hydro Power So losses overall are about 50% 12/14/

17 Hydro Power (resource assessment) 12/14/

18 Hydro Power (resource assessment) 12/14/

19 Hydro Power (resource assessment) 12/14/

20 Hydro Power (resource assessment) 12/14/

21 Discharge (m 3 /s) Hydro Power Percentage of discharge exceeding 12/14/

22 Discharge (m 3 /s) Hydro Power P Q gh e 13,731kWh/m 14,000 kwh/m head head Percentage of discharge exceeding 12/14/

23 Hydro Power C unit energy C annual (24 365) P C O&M installed f plant C unit energy C annual C O&M P installed f plant = Unit energy cost = Annualised cost = Operation and maintenance cost = Installed power = Plant factor 12/14/

24 Hydro Power C C 1 i annual capital n i n 1 i 1 C annual = Annualised cost C capital = Capital cost i = Interest rate n = number of years 12/14/

25 Hydro Power 12/14/

26 Hydro Power Civil works 19% Electromechanical 27% Civil works 13% Electromechanical 48% Penstock 12% Penstock 21% Engineering 12% Distribution 14% Engineering 12% Distribution 6% Nepal Sri Lanka 12/14/

27 Hydro Power (Pakistan) 12/14/

28 Hydro Power (Pakistan) 12/14/

29 Hydro Power (Systems) Hydropower systems may be divided into two ways: Based on its construction methods. There are three types of hydropower systems based on construction methods: Impoundment. Diversion or run of river. Pumped storage. Based on their size Large hydropower (> 30 MW) Small hydropower (100 kw-30 MW) Micro hydropower (<100 kw) 12/14/

30 Hydro Power (Systems) Impoundment Most of the large hydropower systems are impoundment type. A dam is used to store river water in a reservoir. Water released from the reservoir flows through a turbine to generate electricity. The water may be released either to meet changing electricity needs or to maintain a constant reservoir level. 12/14/

31 Hydro Power (Systems) Dam A dam is built to raise the water level of the river to create a falling water system. This also controls the flow of water. The reservoir of a dam basically stores the energy in the form of potential energy. When water flows down from the reservoir into a turbine, this potential energy is converted to kinetic energy that rotates the turbine blades. The main factor that needs to be considered is the ability of the dam to withstand the pressure of water build up behind it. 12/14/

32 Spillways Hydro Power (systems) When dams are designed, provision must be made to cope with large floods. Spillways are pathways for floodwater to flow over or around the dam so that the dam itself is not breached. 12/14/

33 Hydro Power (systems) Run of the River Run-of-the-river plants derive energy from a water flow with minimal disruption of the flow or the surroundings. Normally, such systems are built on small dams that impound little water. They may not cause changes in the water quality. They do not normally affect downstream habitat or terrestrial habitat. Other concerns, such as ladder rejection by fishes, are not problems. 12/14/

34 Hydro Power (systems) Pumped Storage Pumped-storage hydropower systems are operated differently from conventional hydroelectric systems. Although these systems use falling water to generate power in the same manner as a conventional hydroelectric system, water, after falling through the turbine, is collected in a reservoir (called lower reservoir). A reversible turbine that works in both directions is used at the pumped storage facility. When demand for electricity is low, the turbine is operated in the reversible mode to pump the water back to an upper reservoir. Water from the upper reservoir is released to generate power during periods of peak demand. 12/14/

35 Hydro Power (systems) Pumped storage systems actually are net users of electrical energy. The generation and pumping cycles are usually 90% efficient. When other losses, such as friction loss, turbine efficiency, etc., are considered, the overall efficiency is generally around 75%. There are several benefits of a pumped storage system: Improved energy regulation and operation of the supply grid. Creates environmental benefits such as reduced gaseous emissions and has little environmental impact during its operation. Allows flexible and rewarding commercial operations across a variety of electrical power supply scenarios. About 127,000MW of pumped-storage hydro capacity is already operating around the world. 12/14/

36 Hydro Power (Turbines) 12/14/

37 Hydro Power (Turbines) Impulse Turbine The potential energy of the water in the reservoir is changed into kinetic energy of one or more jets. Each jet then hits a series of buckets or cups placed on the perimeter of a vertical wheel. 12/14/

38 Hydro Power (Turbines) 12/14/

39 Hydro Power (Turbines) Although the ideal turbine efficiency is 100%, in practice values range from 50% for small units to 90% for accurately machined large commercial systems. 12/14/

40 Hydro Power (Turbines) It is usually easier to increase the number of nozzles n than to increase the overall size of the turbine, but the arrangement becomes unworkably complicated for n 4. For small wheels, n = 2 is the most common. 12/14/

41 Hydro Power 12/14/

42 Hydro Power (Turbines) 12/14/

43 Hydro Power (Turbines) If the ratio u c /u j is the same for two wheels of different sizes but the same shape, then the whole flow pattern is also the same for both. It follows that all non-dimensional measures of hydraulic performance, such as m and, are the same for impulse turbines with the same ratio of uc/uj. Moreover, for a particular shape of Pelton wheel (specified here by r/r and n), there is a particular combination of operating conditions (specified by ) for maximum efficiency. 12/14/

44 Hydro Power (Turbines) Reaction Turbine 12/14/

45 Hydro Power (Turbines) 12/14/

46 Hydro Power (Turbines) The selection of a turbine depends on several factors. Each turbine operates most efficiently at a certain pressure and flow range. However, often times, the working head determines the turbine types for a specific application. 12/14/

47 Hydro Power 12/14/

48 Hydro Power (Social and Environmental aspects) It produces about 20% of the world s electric power. In at least twenty countries, including Brazil and Norway, hydro-power accounts for over 90% of the total electricity supply. Hydroelectric systems are long lasting with relatively low maintenance requirements. For hydro plant with ample supply of water, the flow can be controlled to produce either base-load or rapidly peaking power as demanded. 12/14/

49 Hydro Power (Social and environmental aspects) Most large dams (i.e. those >15m high) are built for more than one purpose, apart from the significant aim of electricity generation, e.g. water storage for potable supply and irrigation, controlling river flow and mitigating floods, road crossings, leisure activities and fisheries. Over one million people were displaced by the construction of the Three Gorges dam in China, which has a planned capacity of over MW; yet these displaced people may never consider they are, on balance, beneficiaries of the increased power capacity and industrialization. 12/14/

50 Hydro Power (Social and environmental aspects) Some dams have been built on notoriously silt-laden rivers, resulting in the depletion of reservoir volume. Hydro-power, like all renewable energy sources, mitigates emissions of the greenhouse gas CO2 by displacing fossil fuel that would otherwise have been used. However, in some dam projects, in an effort to save construction time and cost, rotting vegetation (mostly trees) have been left in place as dam fills up, which results in significant emissions of methane, another greenhouse gas. 12/14/

51 Classification of hydroelectric power plant 12/14/

52 Thank You 12/14/